Garlic
[Allium sativum] is among the oldest of all cultivated plants. It has
been used as a medicinal agent for thousands of years. It is a
remarkable plant, which has multiple beneficial effects such as
antimicrobial, antithrombotic, hypolipidemic, antiarthritic,
hypoglycemic and antitumor activity. In this review, we will discuss
particularly the largely preclinical use of this agent in the treatment
and prevention of cancer. A number of studies have demonstrated the
chemopreventive activity of garlic by using different garlic
preparations including fresh garlic extract, aged garlic, garlic oil
and a number of organosulfur compounds derived from garlic. The
chemopreventive activity has been attributed to the presence of
organosulfur compounds in garlic. How this is achieved is not fully
understood, but several modes of action have been proposed. These
include its effect on drug metabolizing enzymes, antioxidant properties
and tumor growth inhibition. Most of these studies were carried out in
the animal models. Also, recent research has focused on the
antimutagenic activity of garlic. Recently, it has been observed that
aged garlic extract, but not the fresh garlic extract, exhibited
radical scavenging activity. The two major compounds in aged garlic,
S-allylcysteine and S-allylmercapto-L-cysteine, had the highest radical
scavenging activity. In addition, some organosulfur compounds derived
from garlic, including S-allylcysteine, have been found to retard the
growth of chemically induced and transplantable tumors in several
animal models. Therefore, the consumption of garlic may provide some
kind of protection from cancer development.